SANDIA LAB NEWS

June 1, 2012

Small worlds come into focus with new Sandia instrument

Paul Kotula recently told a colleague at another laboratory that Sandia’s new aberration-corrected scanning transmission electron microscope (AC-STEM) was like a Lamborghini with James Bond features.

PRINCIPAL INVESTIGATORS Paul Kotula, left, and Ping Lu (both 1822) show off Sandia’s new aberration-corrected scanning transmission electron microscope, which has a unique combination of X-ray detectors and very high resolution and is capable of doing analyses in far less time than the Labs’ older analytic microscope. (Photo by Randy Montoya)

The $3.2 million FEI Titan G2 8200 Sandia accepted in February is 50 to 100 times better than what went before in terms of resolution and the time it takes to analyze a sample, say Paul and Ping Lu (both 1822), principal investigators.

Its unique combination of X-ray detectors and very high resolution offers magnification that Paul compares to a telescope powerful enough to show two peas side by side on the moon. Slides of microstructures analyzed with the AC-STEM and Sandia’s older analytical microscope highlight the new capabilities, with a clear image from the AC-STEM and a fuzzy one from its predecessor. An analysis that took seven minutes on the AC-STEM took two hours on the previous instrument, he says.

Ping and Paul operate the microscope from a basement lab adjacent to the environment-controlled room that houses it. They’re not in the same room because the instrument is so sensitive even clicking a computer mouse against a desk would cause an image to jump, Ping says.

“At the atomic scale, it doesn’t take too much,” he says.

Operating unit from 1,000 miles away

The remote operation affords another advantage: Sandia/California researchers can run it from 1,000 miles away, which they demonstrated in March. Paul jokes the only thing they can’t do from California is load the sample and fill the liquid nitrogen that cools the machine.

The AC-STEM delivers electron beams accelerated at voltages from 80 kV to 200 kV, allowing researchers to study properties of structures at the nanoscale — very important for materials science in everything from microelectronics to nuclear weapons.

Any impurities or structural defects hurt performance in super thin microelectronics layers, for example, he says. In the same way, interfaces in a weapon are critical because that’s where any impurities tend to be, “where you might get some sort of separation or corrosion or reaction happening that’s the basis of aging of these materials,” he says. “Being sensitive to that lets us help others predict lifetimes, replacement intervals, or failure modes so we know what to look for.”

It takes powerful instruments to do those studies.

“You need this kind of tool to quantify it,” says Ping as he sits in front of a computer screen showing an image of a 50-nanometer-thick specimen inside the AC-STEM — a sample 2,000 times thinner than the thickness of a human hair.

What looks like a close-up of mesh or lattice on the screen is really an image of 3-angstrom atomic spacing between titanium and strontium. An angstrom equals one 10th of a billionth of a meter.

The microscope uses a unique in-lens design in which four X-ray detectors surround a sample placed in the center, increasing collection efficiency, Ping says.

Older instruments were limited by lens aberrations, particularly spherical aberration that prevents sharp focus because electrons off of the optical axis are focused more strongly than ones near the optical axis, Paul says. The AC-STEM’s additional lenses and computational elements negate that, he says.

“With the aberration-correction technology, you can open the aperture up and keep all those electrons focused to a nice point on your sample,” he says.
Atomic resolution requires a tiny probe and scanning the sample at very high magnification.

Preventing damage to samples

The AC-STEM can put the probe on a sample for tens of microseconds or even milliseconds and gather enough information for researchers to tell what elements are present at atomic resolutions, Paul says. The probe returns to the same spot repeatedly with a drift correction that prevents a blurred image, collecting a stream of X-ray photons while minimizing damage since short duration equals a smaller dose rate.

High electron beam currents can damage some samples. However, “you can easily back off on the intensity” of the AC-STEM’s beam because it has so many adjustable parameters, Paul says.

A dark spot that looks like a hole in Ping’s sample indicates damage, but it’s deliberate as he sputters atoms from the sample with a 200kV electron beam, knocking atoms out of the lattice to measure how removing part of the sample affects the X-ray signal.

The AC-STEM also studies material in the micron world. Although a hundred microns is about the smallest size a human eye can see, it’s a huge scale for a transmission electron microscope.

At the micron level, “we’re not making such a fine beam anymore but we’re using the collection efficiency and the bright electron source to be able to be sensitive to small concentrations,” Paul says. “That’s very important for a lot of our customers who are looking for impurities in some of these materials.”

First commercial unit fielded

The room that houses the microscope has to remain stable in terms of vibration, acoustics, temperature, and electromagnetic fields. Acoustic and chilled water panels line the walls, and the room’s 65-degree temperature varies less than a tenth of a degree Celsius over half an hour. The instrument’s accelerator, capable of producing 200,000 volts, is stowed behind acoustic drapes in a corner to isolate vibrations from the 9.5-foot-tall column containing various types of lenses and the instrument’s in-lens X-ray detectors.

Sandia’s AC-STEM is the first commercial unit fielded, based in part on development funded by a DOE Basic Energy Sciences project aimed at developing advanced electron microscopes built around aberration-correcting optics. The Transmission Electron Aberration-corrected Microscope, or TEAM project, was a collaboration involving the Argonne, Brookhaven, Lawrence Berkeley, and Oak Ridge national laboratories and Frederick Seitz Materials Research Laboratory.

The concept was theorized in the 1950s but computers were in their infancy and no one could manually adjust microscopes requiring multiple alignments and mechanical and power stability, Paul says.

The AC-STEM offers endless potential for collaboration with colleagues in the Labs and at other national laboratories, companies, and universities since they don’t have to be on site to participate, the researchers say

The tool makes it easier to conduct a quick, basic analysis of energy storage options and determine the value of energy storage technologies for a specified application. This, developers say, will increase the adoption of energy storage technologies.

“ES-Select is the first of a suite of easily accessible web tools to help potential users and regulators make decisions on energy storage options in specific applications,” says Imre Gyuk, program manager of DOE’s Energy Storage program.

The application is available for free download on Sandia’s energy storage website at www.sandia.gov/ess.

“This tool is designed to help users understand at a basic level what storage can do. If it looks beneficial from a cost standpoint, they can explore the options further,” says Sandia project manager Dhruv Bhatnagar (6113).

Utilities and developers who want to use energy storage have many technologies to consider, including flywheels, compressed air, pumped hydro and thermal storage, and six types of electric batteries. All have different costs, and estimating revenue from using various applications is difficult. Researching all relevant cost factors independently previously took days or weeks, but ES-Select aggregates all relevant factors into a single decision-support tool that runs in a few minutes. If the results are favorable for a particular technology, users can determine whether to run detailed, site-specific analysis using other tools.

“ES-Select is an educational and decision-support tool for deployment of energy storage on the power grid,” says Ali Nourai, executive consultant for DNV-KEMA, and co-developer of ES-Select. “It has been created for public use to promote the understanding of storage technologies and the benefits they offer when applied on the electric grid.”

The tool aids decisions about what storage technologies would work best in a given situation. For example, if a business pays more for electricity during the day than at night, the owner could use the tool to quickly evaluate several energy storage options to determine the cost-benefit of buying lower-cost electricity at night and storing it for use during the day.

Users can input the application they are interested in, as well as such parameters as energy costs and discount rates. The program produces a list of storage technologies and their predicted benefits and associated costs. ES-Select aggregates all of the inputs and assumptions — monetary value for an application, technology costs, performance characteristics, and operation and maintenance costs — and quickly spits out recommended options.

Rather than basing decisions on a single factor such as capital cost, ES-Select assesses how an energy storage technology performs while addressing uncertainties in application value, storage cost, cycle life, efficiency, discharge duration, and other parameters.

“With funding from DOE’s Energy Storage Program, Sandia has worked with KEMA to develop a user-friendly, freely accessible tool to evaluate potential applications of energy storage,” says Gyuk. “We hope that this tool will contribute to the widespread adoption of storage on the grid.”

ES-Select should benefit utilities, independent power producers, industrial and commercial enterprises, regulators, lawmakers, and the public, including those doing research on energy storage. “We’ve already had a lot of people asking about this program, and we know many are eager to use it,” says Dhruv. “I think this will encourage those who might not have considered energy storage before to think more seriously about it and evaluate its potential as a viable option.” -- Stephanie Hobby

Sandia helping nation find best way to protect infrastructure, recover from disasters

Sandia is trying to anticipate the unexpected to help the nation prepare for severe weather and figure out the best way to lessen the havoc hurricanes and other disasters leave on power grids, bridges, roads, and everything else in their path.

HURRICANE WATCH — The Department of Homeland Security’s National Infrastructure Simulation and Analysis Center (NISAC), housed at Sandia and Los Alamos national laboratories, provided timely analysis of the potential infrastructure impacts of Hurricane Irene in August 2011. Officials asked NISAC to analyze Irene’s likely impacts while the storm moved toward shore and to deliver an analysis in less than 12 hours. NISAC came through; its analysis was used to brief FEMA and first responders as well as the DHS and DOE.

“I think our work in critical infrastructure protection is a really great thing to be working on. We can help provide the understanding and information to help policymakers make good decisions” that result in more resilient infrastructure — meaning it’s better able to absorb impacts and recover quickly, says Marianne Walck, director of Geoscience Climate and Consequence Effects Center 6900.

Marianne was part of a panel in early May at the American Geophysical Union’s inaugural Science Policy Conference aimed at highlighting geoscience insights for the economy, public safety, and national security. She discussed Sandia’s work in developing ways to assess the resiliency of the nation’s infrastructure and in providing the knowledge officials need to create more resilient systems.

Sandia is trying to make the effort more quantitative by developing a mathematically rigorous approach to assess resilience objectively, says manager Lori Parrott (6924). As a part of critical infrastructure protection programs funded by DOE, the US Department of Homeland Security (DHS), Sandia’s Laboratory Directed Research and Development program, and agencies such as the Federal Emergency Management Agency (FEMA), Sandia has developed capabilities ranging from high-fidelity models of individual infrastructure elements to generic network models and dynamic simulations.

“The analytic information can allow policymakers to be better informed to decide how to craft policies, how to promote incentives to create resilient infrastructure, or how to prioritize recovery and restoration,” she says. “It’s a true example of leveraging federal investments in Sandia capabilities to support multiple agencies’ missions.”

Researchers do a risk analysis and quantify uncertainties. They look at interdependencies among systems and supply chains, the resilience of various systems, how infrastructure systems fail, any cascading effects, and how results might differ if there are a series of disasters instead of just one.

Good models allow analysts to quantify consequences of disruptions in very complex systems. “If you don’t have a good model to look at or to exercise in terms of running through these various scenarios, you may not understand what could really happen,” Marianne says.

A flood, for example, could damage roads, collapse bridges, and take down power lines, leaving officials to decide how best to rebuild and how much that will cost, Marianne says.

“This isn’t just saying, ‘Oh, I think that hurricane is going to knock out this particular chemical plant.’ Then you have to think about what that means in terms of getting critical chemicals to industries. What societal or economic effects will result if this particular product isn’t supplied? There are lots of different interactions that go on,” she says. “It’s just illuminating to understand what the impacts are if you’ve got particular types of infrastructure.”

Understanding impacts

Efforts to analyze natural disasters and other threats grew out of Sandia’s strengths in systems engineering and complex systems analysis, she says. Some of the work is done through the National Infrastructure Simulation and Analysis Center (NISAC), a DHS program housed at Sandia and Los Alamos national laboratories. NISAC models and analyzes critical infrastructure, including how interdependent and vulnerable systems may be and the consequences of having them disrupted.

“Given how much of our national and economic security rests on the resiliency of our infrastructure, the rational choice for policy-makers is to experiment with models, not the system,” Lori says.

Each year, NISAC undertakes projects to analyze various risks. Given a particular incident, how could people be evacuated given a particular road system? How much damage would hurricane-force winds cause to power lines, and would that cause governments to consider requiring underground lines in the future? There also are rebuilding considerations. Would it be better, for example, to focus on repairing rail transportation routes in a particular area rather than try to repair all routes simultaneously?

NISAC has developed expertise in analyzing subjects and developing models based on that analysis that cover everything from national transportation to interdependent supply chains. “Through our long-term analysis projects and our capability development, we work to keep our data, models, and analytic expertise current to be useful for crisis decision support,” Lori says.

For example, NISAC has worked on a number of hurricanes, including Hurricane Irene, the only hurricane to threaten the US mainland last year. Although a small storm compared to other hurricanes, Irene was unusual. Rather than striking a concentrated area, Irene traveled up the East Coast, threatening a large swath of significant infrastructure.

Officials asked NISAC to analyze Irene’s likely impacts while the storm moved toward shore and to deliver an analysis in less than 12 hours. NISAC came through, and Marianne says its analysis was used to brief FEMA and first responders as well as the DHS and DOE. -- Sue Major Holmes